The present invention generally relates to releasing devices, and more particularly, releasing devices employing bimetals, which releasing devices are conventionally useful to actuate various fire protection equipment in response to increases in heat in the vicinity of the device.
Conventionally, fusible or meltable releasing devices have been employed, such as fusible links in cables which are held under tension in normal conditions and which are actuated by the melting of the link and the resulting break of the cable.
More recently, bimetallic links, such as those illustrated in my previously issued U.S. Pat. Nos. 3,889,314 entitled, "Heat Actuated Link", and 3,725,972 entitled, "Fire Link and Method of Actuating Same", have been described wherein a mounting element having a bimetallic strip attached thereto, which cooperates therewith, may engage a pawl having an aperture therein which is engaged by the bimetallic element in the normal position and which is released thereby as the tip of the bimetallic element separates from the mounting or striker portion thereof to release the pawl. These bimetallic links have conventionally been installed by attaching a cable to either the pawl, the mounting element, or both in a manner similar to that used for the fusible or meltable links described above. These bimetallic links have exhibited certain advantages over the prior art fusible links in that following a return to normal temperatures, the link may be reset simply by reinserting the pawl into the remaining link assembly.
Unfortunately, prior art devices of the type described above have required that access be provided to the link device so that manual resetting is possible. In certain installations, such as in smoke tunnels, ducts, plenums, etc., human access to reset or replace releasing devices is limited. Additionally, relatively skilled personnel must be employed in order to reset or replace the aforementioned releasing devices. In the case of the bimetallic links, these people must as least understand the proper method of inserting the pawl so that is is properly gripped by the remaining portion of the link.
For one approach to this problem, please refer to my previously issued United States patent entitled, "Remotely Resettable Fire Damper", U.S. Pat. No. 3,796,248, dated Mar. 12, 1974.
In addition to the desirability of having fire links which are remotely actuatable and resettable, it is desirable to provide a resettable fire actuatable releasing device which is responsive to power failures.